The present invention relates to a solenoid-operated, poppet-type orifice control valve.
Poppet-type valves have traditionally been used as on/off valves or for pressure control, while spool valves have been traditionally used for precision control. However, since poppet-type valves are less prone to contamination, there is a desire to use poppet-type valves for precision control as well.
An example of a poppet-type control valve is found in U.S. Pat. No. 3,893,471 issued to Byers, Jr. in 1975. Such valves have a pressure balancing pin which is used to cancel out the effects of load due to pressure on the main orifice control valve, thus making the valve insensitive to load variations. However, in such a valve, when its solenoid is off, there is a fluid leakage path from inlet to outlet between the pressure balancing pin and the armature. Such leakage is acceptable when the solenoid is "on" and the valve is open. However, when the solenoid is off, such leakage can lead to "drift" of the actuator or device controlled by the valve. Therefore, it would be desirable to have a poppet-type control valve wherein such leakage is prevented when the valve is closed.